In recent years, various electrochemical sensors have been developed for usage such as the detection or quantitative determination of a specific component in the patient's bodily fluid such as blood. For example, known is a subcutaneous implant-type sensor which implants an electrochemical sensor under the patient's skin and continuously measures the target substance (specific component) contained in the specimen over a predetermined period of time. As an example of the subcutaneous implant-type sensor, there is a subcutaneous implant-type glucose sensor. With the subcutaneous implant-type glucose sensor, the specimen to be measured is the interstitial fluid, blood or the like existing outside the cells of the subcutaneous tissue. Moreover, a continuous glucose monitoring (CGM) device capable of continuously monitoring the glucose level by using this type of subcutaneous implant-type glucose sensor has also been developed.
As one mode of the subcutaneous implant-type sensor, there is a type comprising a sensor electrode formed on the tip side of a flexible, elongated sensor substrate based on the thin film masking technique, and a conductive contact pad formed on the base end side of the sensor substrate. This conductive contact pad is, for example, electrically connected to an appropriate measurement device according to a conventional method via an electrical wiring.
Normally, the base end side of the subcutaneous implant-type sensor to which the conductive contact pad is formed is disposed outside the body by being housed in a sensor housing (also referred to as a case or casing). Moreover, the sensor housing is attached to the skin, for example, by appropriate adhesive means such as an adhesive tape provided to the lower surface thereof. In addition, the tip side of the subcutaneous implant-type sensor where the sensor electrode is disposed penetrates the skin according to an appropriate method, and the sensor electrode formed on the tip side is percutaneously disposed under the skin. When the monitoring of the target substance is complete, the tip side of the sensor that is implanted under the skin is extracted outside the body.
Here, a user (for example, a patient or a physician) handling the subcutaneous implant-type sensor will demand user-friendliness of being able to easily insert (implant) the sensor under the skin. As related technology, for example, Patent document 1 discloses an insertion set for a percutaneous sensor, and Patent document 2 discloses a percutaneous specimen sensor assembly.    Patent document 1: Japanese Translation of PCT Application No. 2002-503988    Patent document 2: Japanese Translation of PCT Application No. 2008-506468    Patent document 3: Japanese Translation of PCT Application No. 2005-520648
With the foregoing conventional technologies, the tip side of the sensor to which the sensor electrode is formed is inserted under the skin together with an insertion needle. Subsequently, only the insertion needle is pulled outside the body in a state of disposing the sensor electrode at a predetermined position under the skin, and the measurement of the target substance is thereafter started. Nevertheless, with the insertion set described in Patent document 1, the insertion needle to which the patient's bodily fluid had adhered upon pulling the insertion needle outside the body is exposed to the outside. Thus, when a third party other than the patient such as the physician performs the operation of pulling out the insertion needle, the physician may come in contact with the patient's bodily fluid and get infected. Moreover, it is necessary to take separate measures for preventing the infection, and the handling of the subcutaneous implant-type sensor by the user becomes complicated, thereby deteriorating the user-friendliness.
Moreover, Patent document 2 discloses a component referred to as an applicator that enables the insertion of the sensor and needle. According to this applicator, the needle is not exposed to the outside upon pulling out the needle from under the skin. However, the applicator is a special component for inserting the subcutaneous implant-type sensor under the skin. Accordingly, in order to start the measurement, after removing the applicator from the mounting unit which serves as the housing, it is necessary to mount an electronic unit housing a sensor electronic device for processing the specimen data of the subcutaneous implant-type sensor on the mounting unit in place of the applicator. Accordingly, since the replacement of equipment is required during the insertion of the subcutaneous implant-type sensor and during the measurement of the target substance, it cannot be said that this is user friendly, and the probability of human error caused by the complication of the operation process will increase.
Moreover, in both of the foregoing conventional technologies, no special devisal is provided for improving the user-friendliness of users upon pulling out (extracting) the subcutaneous implant-type sensor from under the skin after the monitoring of the target substance is complete. In other words, the mode of the foregoing conventional technologies is to pull out the subcutaneous implant-type sensor from under the skin by removing the sensor housing while peeling the adhesive tape from the skin. Thus, when an inexperienced person attempts to pull out the subcutaneous implant-type sensor, there is a possibility that the user will suffer pain or the sensor will become damaged as a result of the strength of pulling out the sensor or the direction of applying the strength being unstable.